The assessment of optical hazards in recent years has led to the recognition of the possible hazards to the retina associated with blue light. Generally speaking blue light has a wavelength in the range of about 400-500 nm. If the blue light hazard is a real threat to vision, then the UV/visible transmission characteristics of ophthalmic lenses, and intraocular lenses (IOLs) in particular, should be modified to provide adequate protection from blue light hazards encountered in the environment.
In the ambient environment solar radiation is the primary hazard to vision. The sun freely emits UV, visible and IR radiation much of which is absorbed by the atmosphere. The solar radiation that is transmitted through the atmosphere and reaches the earth's surface consists of UV-B radiation (230-300 nm), near UV or UV-A radiation (300-400 nm), visible light (400-700 nm) and near IR radiation (700-1400 nm). The ocular media of man in its normal, healthy state freely transmits near IR and most of the visible spectrum to the retina. UV-B radiation is, however, absorbed by the cornea and does not reach the retina. UV-A, and the blue portion of the visible spectrum can be absorbed by the crystalline lens of the eye depending upon the person's age.
The human crystalline lens changes its UV and visible transmission characteristics as it ages. In infancy the human lens will freely transmit near UV and visible light above 300 nm, but with further aging the action of UV radiation from the environment causes the production of yellow pigments, fluorogens, within the lens. By approximately the age of 54 the lens will not transmit light below 400 nm and the transmission of light between 400 and 500 nm is greatly diminished. As the lens ages it continuously develops a yellow color, increasing its capacity to filter out near UV and blue light.
Currently, IOLs capable of blocking UV and blue light to varying degrees are effective under certain conditions. However, there are some major drawbacks with such IOLs:                1. Patients with blue light blocking IOLs experience reduced vision quality in dim light conditions. The presence of a blue light blocking chromophore in the lens of the IOL interferes with scotopic vision (low light conditions). This is due to the natural reaction of the eye in scotopic conditions where the pupil dilates to accommodate more light. At the same time, a greater amount of IOL surface area is exposed to the incident light causing an incremental increase of blue light filtration efficiency and an overall reduction in contrast sensitivity.        2. The presence of blue light blocking chromophore in e.g., IOLs, reduces contrast sensitivity in some cases.        
Due to their yellow color (which the presence of blue light chromophores imparts to IOLs), blue light blocking chromophores in IOLs and other ophthalmic devices may interfere with color perception.